After some 10 minutes of power on a buzzing sound of paper into a fan emereged from the PSU unit, followed shortly by a white smoke. The smell reminds me of my paper burning experiments as a child.
A possible sign of the upcoming problem could have been the unstable signal measured on the display, but since I had cleaned boards the problem could have been somewhere else.
I suspect a failure in a PSU capacitor, but I am not going to troubleshoot it.
R.I.P. Gould 4072.
Edit 2014-02-11: I do not own anymore the Gould 4072.